In these days of escalating prices, paper currency acceptors have become well known, their usage being commonly applied to vending machines and the like, which often require deposit of money in amounts inconvenient to carry in coin Examples of such units can be found in my U.S. Pat. No. 4,884,671 and in the patents cited therein.
Since these paper currency acceptors are used for the unattended collection of money, usually in connection with the sale of goods, the users of these devices who are inclined to larceny are often in situations where their attempts to defraud such currency acceptors will not be observed. One of the simplest manners of defrauding such devices, known as "stringing", involves the attachment of a "leash" to a legitimate bank note. The leash is most commonly a piece of string taped to the bill, but may also be wire, long strips of tape, mylar ribbons or the like, and other means for attachment may likewise be substituted. The defrauder will typically deposit the modified bill into a currency acceptor, and use the leash to pull the bank note therefrom after using the credit accrued from the deposit and validation of the otherwise legitimate security. Obviously, the susceptability of paper currency acceptors to this manner of defrauding constitutes a serious problem.
Numerous attempts have been made to solve this problem such as providing a slotted drum in the transport path of the currency, the slot in the drum defining a portion of the pathway. After the bill passes through the slotted drum, the drum is rotated to a position where the slot is out of alignment with the pathway so that the pathway is occluded and the note cannot pass reversely therethrough. Such a system requires components that are costly to manufacture and assemble, and requires precision positioning means to ensure that the drum slot is properly aligned with the currency passageway.
Other attempts to solve the problem employ paired meshing transport rollers which are made of resilient material, and are strongly biased against one another to effectuate tightly gripping engagement with the deposited bank note passing therethrough. Such systems are subject to accelerated wear of these transport rollers, thus reducing their grip upon the bank note. The transport rollers of such a mechanism are subject to the accumulation of containments from the processed bills, thus requiring frequent cleaning to maintain necessary friction. Accordingly, if such systems are not maintained frequently, they can become susceptible to such defrauding schemes.
Consequently, a need exists for a paper currency acceptor having an antifraud device which is easy and inexpensive to manufacture and assemble, requires little or no maintenance, and is positively resistant to stringing.